I am think of insulating the flue of my wood burning stove because I sometimes get condensation in the flue. I all ways have good dry wood and run the stove at the recommended temp. The problem seems to be mostly when the stove isnt going or shut down over night. It will have to be of the back fill type. I have heard that if vermiculite gets wet or draws moisture from damp masonry it becomes a solid spongy mess and is difficult to remove if the liner needs replaced in the future. So the questions are
Is there a better back fill insulation that does not become a problem
Is there another way of avoiding the small amount of condensation
Is there a better back fill insulation that does not become a problem
Is there another way of avoiding the small amount of condensation